a) Field of the Invention
The present invention relates to the repair of a leak in a piping system, and more particularly a method for repairing a leak at a connection of a branch pipe to a main pipe. The present invention relates to the apparatus and components for making such a repair, and also relates to the repair structure itself that is made in accordance with the present invention.
b) Background Invention
There are various industrial environments where there exists a pipe system with one or more main pipes and a plurality of branch pipes connected thereto. One of the more vulnerable connections which can experience the formation of a leak or leaks is where a branch pipe connects to a main pipe, and particularly where there is a socket welded connection.
In the nuclear power industry pipe systems are used for the circulation of liquid (i.e. water), and branch connections are normally used for piping vent and drain connections, as well as instrumentation connections. The socket welded connection is often made by a branch fitting, such as a sockolet, half-coupling, or pipet. Typical connections are branch pipes having, for example, one inch or a three quarter to one inch nominal pipe size. Quite often the failures that lead to the leak are due to fatigue of the socket welded connections. Once a crack is initiated in a weld or pipe, normal plant steady state vibrations can drive the crack through the wall of the fittings and/or pipe.
Typically, in the prior art, for the repair to be made to the leak, it is necessary that the system be isolated and a shutdown is required to make the repair. If the large pipe system cannot be isolated due to either leaking valves or there being no isolation capability, a repair becomes extremely difficult. In water systems, a freeze seal can be used to provide proper isolation. However, freeze seals are difficult and take a significant period of time to establish large bore piping. Thus, in some cases freeze seals are impractical.
A search of the patent literature has revealed a number of U.S. patents, and these are discussed below.
U.S. Pat. No. 6,116,285 (Wilson) shows a pipe plug that is screwed into a nipple secured to the side of a pipe.
U.S. Pat. No. 5,884,668 (Larkin) shows a plumbing tool for temporarily plugging a pipe, and particularly for plugging water pipes, gas pipes and the like, which normally contain fluid or gas under pressure. In column 1, the patent discusses the problem that when a pipe is wet it is impossible to obtain a watertight solder joint. To alleviate this problem, this device permits the temporary plugging of a water pipe where the plug can be inserted through the bore of a plumbing valve to plug the pipe, so as to permit the valve to be de-soldered from the pipe and removed and replaced while the plug is in its position blocking the flow of water or gas in the pipe. There is an expandable gasket 21, which is positioned between a lower washer 15 and an upper washer 13. By manipulating the two nuts 11 and 23, the sleeve 9 is pressed downwardly against the washer 13 to compress, and thus expand, the expandable gasket 21. As shown in FIGS. 3 and 4, this tool can be inserted through the valve and downwardly into a location to plug the pipe.
U.S. Pat. No. 5,590,676 (Wagner) shows a system for the installation of a permanent stopper or plug to prevent the escape of gas under pressure from a pipe. FIG. 1 shows a preliminary step for a tapping machine (designated xe2x80x9cTxe2x80x9d) to be inserted through an existing gate valve V to drill the hole in the pipe P to ensure that the hole is round. After this is done, the tapping tool T is removed, and the gate valve closed. Then the apparatus 10, is utilized to insert the permanent plug.
U.S. Pat. No. 5,363,881 (Larkin) shows an expanding pipe plugging device in which a threaded nut and rod are used to compress and expand the locking element.
U.S. Pat. No. 5,038,818 (Jiles) shows an apparatus to repair a leak in a gas pipe. This is accomplished by mounting two fixtures 200 on opposite sides of the leak 101 in the pipe. The next step is to drill two holes at the location of each fixture 200. At this point, the bypass of the gas flowing in the pipe travels through the line 107, and now the repair of the leak 101 can take place. With that accomplished, the next task is to provide a permanent plug for the two openings that have been drilled. The first method is shown in FIGS. 18 through 22. There is the elastomeric plug 843 which is pressed between upper and lower compression plates 845 and 847 to form the seal. In an alternative procedure, after the fixtures 200 are removed, the polyethylene caps may be screwed or fused onto the branching saddle pipe stubs 113 to provide a backup seal. The alternative method for insertion of the completion plug assembly 900 is illustrated in FIGS. 23 and 24.
U.S. Pat. No. 4,127,141 (Ledonne et al) shows a means for closing off a fluid pressure carrying pipe while repairs are being made. There is a valve secured to the opening being repaired through which an expansion element is passed and expanded to obstruct the side wall opening in the pipe, so there""s no loss while repairs are carried out.
U.S. Pat. No. 4,249,577 (Davis) shows a method for sealing gas lines. The sequence of steps is shown in FIGS. 6 through 16. As shown in FIGS. 8 and 9, a temporary plug is installed. In FIGS. 11 through 16, there are shown the steps by which a permanent plug can be placed in the opening and welded.
U.S. Pat. No. 2,690,612 (Scott) shows a means for accessing the interior of a pressure or vacuum vessel by passing a threaded rod and nut locking means through a gate valve into an opening that is to be closed.
U.S. Pat. No. 2,621,679 (Tuttle) shows a method and means for attaching a test plug to a pipe end. There are mechanical means to secure the test plug to the outside of the pipe and expanding elements 36, and 38, which seal against the inside of the pipe so test pressure may be applied.
U.S. Pat. No. 2,176,260 (Johnson) shows a means for obstructing an outlet by means of an expandable rubber plug for obstructing an outlet from a water main so that a service line may be worked on.
U.S. Pat. No. 2,170,866 (McAllister) shows a generic expansion stopper for use with pipes, tanks or the like.
U.S. Pat. No. 2,141,274 Lenhart) shows a means for blocking a pipe so that valves or other fitments may be repaired.
U.S. Pat. No. 1,850,040 (Turner) shows a plugging element 6 that is compressed within a service line to prevent access to the gas service line.
U.S. Pat. No. 1,083,024 (Morris) shows a plug carrying saddle fitting that is secured to a pipe, for access to the pipe.
The method, system, apparatus and components of the present invention are particularly designed for repairing a leak in a pipe assembly which comprises a main pipe with a main pipe wall having a main pipe connecting portion with a through opening and a branch connecting to the main pipe at the through opening.
The present invention is designed to enable the repair to be made without the necessity of draining the water or other liquid from the main pipe at which the repair is being made. Further, the present invention enables the repair to be made with either a permanent plug shutting off the branch opening or making a connection to the same branch pipe, or another branch pipe. This can be done in a manner so that the repair structure meets the strictest standards (ASME: American Society of Mechanical Engineers, and ANSI: American National Standard Institute) relative to durability and resistance to development of cracks due to the fatigue or application of exterior forces.
In the method of the present invention, the first step is to separate the branch pipe from the main pipe. Then a plugging tool is provided with a plug portion and a plugging tool extension. The plug portion of the tool is inserted into the through opening of the main pipe, with the plugging tool extension extending outwardly from the main pipe. This provides blockage of the fluid flow from the opening.
There is provided an intermediate connecting section which has a through passageway and a connecting end portion. The intermediate connecting section is positioned so that the plugging tool extension is located in the through passageway of the intermediate connecting section.
The connecting end portion of the intermediate connection section is then joined (e.g. by welding) to the connecting portion of the main pipe desirably by inserting the connecting end portion at least partly into the through opening of the connecting portion of the main pipe. After this, the plug portion is removed from the through opening of the connecting portion by withdrawing the plugging tool extension with the plug portion, after which a closure member is used to close the through passageway of the intermediate connection section.
In a preferred embodiment, the plug member is inserted into the through opening of the connecting portion, and the extension member is manipulated to expand the plug member in the through opening of the connecting portion to form a fluid type seal. Subsequently, the extension member is manipulated to collapse the plug portion to then withdraw the plug portion from the through opening.
Also in a preferred form, the connecting end portion of the intermediate connecting section is placed in interfitting relationship with the connecting portion by inserting the connecting end portion at least partly into the through opening of the main pipe connecting portion of the main pipe.
More specifically, the through opening of the main pipe connecting portion comprises a first opening portion of a smaller diameter closer to a center location of the main pipe, and a second larger diameter opening portion positioned further from the center location of the main pipe. The method further comprises inserting the plug member into the first opening portion of the through opening, and positioning the connecting end portion of the intermediate connecting section into the second opening portion of said through opening of the connecting portion.
In a preferred form, the connecting portion of the main pipe has an annular surface portion facing generally outwardly from the center location of the main pipe and surrounding the second larger diameter opening portion. The method further comprises applying a bonding agent at a circumferential location of the annular surface portion and at an adjacent surrounding surface portion of the connecting end portion of the intermediate connecting section. In a preferred embodiment, the bonding agent is a weld material which is applied circumferentially to the annular surface portion and also to the adjacent surface portion and the connecting end portion.
The intermediate connecting portion has a second connecting end portion and a central connecting portion located between the connecting end portion and the second connecting end portion. The connecting end portion has a wall thickness of a first smaller thickness dimension and said central intermediate connecting portion has a wall thickness of a greater thickness dimension at a location adjacent to the annular surface portion. The annular surface and an adjacent portion of the central portion connecting portion form a circumferential recess in which the bonding agent is placed.
Further, in the method of the present invention, the plug member is removed from the through opening of the main pipe section and outwardly through the through passageway of the intermediate connecting section. The method further comprising placing a closure plug in the through passageway at the second end portion of the intermediate connecting section to block liquid flow through the passageway of the intermediate connecting section. More specifically, the second end portion of the intermediate connecting section has a generally cylindrical outer end recess to receive the closure plug, and the closure plug has a threaded connection in the recess. Desirably the second end portion of the intermediate connecting section has an outer annular recess surrounding the outer end recess of the second end portion, and the outer annular surface faces outwardly from a center location of the main pipe. The closure plug extends outwardly beyond the outer annular surface as an outer generally cylindrical closure portion. The method further comprises applying a bonding material to the outer annular surface and also to an adjacent portion of the outer generally cylindrical closure portion. Desirably the bonding agent is a weld material.
Also in a preferred form the threaded portion of the cylindrical recess is spaced toward the center location of the main pipe from the outer annular surface of the second end portion so that there is a substantially flat cylindrical surface portion of the recess at the second end portion which is adjacent to the outer annular surface surrounding the recess of the second end portion, and extending therefrom to said threaded connecting portion.
Other features of the present invention will become apparent from the following detailed description.